Application and Ar-Ar Calibration of Uranium-Series Dating at Olorgesailie

在美国国家科学基金会的支持下。Kenneth Ludwig， Alan Deino和Warren Sharp将从肯尼亚南部经典的Olorgesailie考古地区收集和分析氩氩定年的样本，并分析铀系列定年的现有样本。奥洛格塞利有着极其丰富的早期人类人工制品的积累和人类居住的连续记录，人们对它的研究已经有50多年了，最近由史密森学会的理查德·波茨和他的同事们正在进行的研究。奥洛格塞利60万年前的记录现在已经确定了年代，这是之前由迪诺进行的氩-氩定年的结果。然而，这些记录中较年轻的部分，包含了从阿舍利技术（一种相对原始的石器工业，以脑容量相对较小的直立人为特征）过渡到中石器时代技术（与解剖学上接近现代的人类有关）的极少数记录之一，现在才得到详细研究。然而，对于奥洛格塞列地层的这一部分，几乎没有任何类型的测年资料，而且精度都不高。我们将通过对这项建议的研究来填补这一空白，部分方法是将一种相对较新的但经过充分验证的高精度方法- -热电离质谱法铀系- -应用于已证明在奥洛格塞利普遍存在的新型样品。这些新类型的样品——其中最有希望的是已经被蛋白石形式的二氧化硅所取代的根铸型样品——以前从未用于铀系列的测年，因此它们的可靠性和准确性尚未得到证实。幸运的是（也是非常不寻常的），这种验证可以在Olorgesailie进行，因为铀系列测年的样本与氩-氩测年的火山灰样本经常共存，后者是公认的考古测年的“黄金标准”，时间范围为5万年至数百万年。如果得到验证，那么铀系列测年法就可以用来对那些缺乏适合氩-氩测年的灰层的较年轻的奥洛格塞利岩层的部分提供年龄控制。有了这项研究提供的预期的年龄控制，史密森学会的科学家们（他们最近获得了一项为期5年的国家科学基金会资助，在奥洛格塞利继续他们的研究）对东非人类文化和行为的进化进行的详细研究将获得一个非常宝贵和精确的年龄控制维度，这在过去50万年的长期人类进化的单点研究中是前所未有的。因此，该项目将与其他联邦资助的研究高度协同（特别是考虑到该项目的费用分摊程度很大），并为勤工俭学的学生提供在考古学和地质学中应用高科技方法的宝贵经验。

With support from the National Science Foundation, Drs. Kenneth Ludwig, Alan Deino, and Warren Sharp will collect and analyze samples for Argon-Argon dating, and analyze existing samples for uranium-series dating, from the classic Olorgesailie archeological area in southern Kenya. Olorgesailie, with its extremely rich accumulation of early human artefacts and continuous record of human occupation, has been studied for over 50 years, most recently by the ongoing studies or Richard Potts and colleagues at the Smithsonian Institution. The pre-600,000 year record at Olorgesailie is now well-dated, as the result of previous Argon-Argon dating by Deino. However, the younger part of the record, which contains one of the very few records of the transition from Acheulean technology (a relatively crude stone industry characteristic of relatively small-brained Homo Erectus) to Middle Stone Age technology (related to anatomically near-modern humans) of is only now being studied in detail. Few dates of any kind are available for this part of the Olorgesailie stratigraphy, however, and none of high precision. It is just this gap which we will fill with the research of this proposal, in part by applying a relatively new but well-validated and extremely high-precision method - uranium-series by thermal ionization mass spectrometry - to new types of samples that have been shown to be common at Olorgesailie. These new types of samples - of which the most promising is root-casts which have been replaced by the opal form of silica - have not been used before for Uranium-series dating, so their reliability and accuracy are unvalidated. Fortunately (and very unusually), such validation can be carried out at Olorgesailie because of the common co-occurrence of samples for uranium-series dating with samples of volcanic ash for Argon-Argon dating, the latter being the acknowledged "gold standard" for archaeological dating in the time-range of 50,000 years to millions of years. If validated, the uranium-series dates can then be used to provide age control on those parts of the younger Olorgesailie beds that lack ash beds suitable for Argon-Argon dating. With the anticipated age control provided by this research, the detailed studies by Smithsonian Institute scientists (who recently obtained a 5-year National Science Foundation grant to continue their research at Olorgesailie) on the evolution of human culture and behavior in East Africa will gain an invaluable and precise dimension of age control at a level that is unprecedented in a single-site study of long-term human evolution over the past 500,000 years. This project will thus by highly synergistic with other federally-funded research (especially given the significant degree of cost sharing of this project), as well as providing valuable experience to a work-study student in applied high-technology methods in archeology and geology.